Pipe freezers are used in the repair or replacement of pipe sections or for repairing or adding fittings to existing pipe installations. Such systems are primarily used in fluid systems where it is not convenient or not readily possible to drain fluid in the pipe installation. By freezing the fluid in the pipe, it is possible to block the fluid in the section of pipe of interest by creating an ice plug.
U.S. Pat. Nos. 5,548,965 and 6,598,412, which are assigned to the assignee of the current invention, use a refrigeration system with evaporator heads or adapters that are sized to fit various standard pipe diameters. The evaporator heads are connected to a portable condenser/compressor unit by flexible coaxial tubes that cycles refrigerant to and from the evaporation chambers. The refrigerant causes the evaporator heads to freeze the pipe where they are in contact.
Although the above patents provide different size openings in the evaporator head to fit different size standard pipes, the systems disclosed therein were not capable of handling pipe diameters of four inches or larger (i.e., large diameter pipes) since the volume of water in such large diameter pipes did not allow for a sufficient removal of heat energy to cause freezing of the liquid.
For example, it has been determined that in order to freeze a four inch diameter pipe sufficiently to create and maintain an ice plug, a temperature of −55 degrees F. must be applied to the pipe. Conventional portable condensers are not capable of creating such a low temperature consistently. So instead, prior systems had to revert to two stage cooling systems, where a first cooling system is used to cool the system fluid, and a second cooling system is used to cool the first system. Because of the high costs of such systems, conventional systems generally rely on the use of liquid nitrogen, compressed air with vortex tubes, or CO2. However, those systems are difficult to use and costly.
A need therefore exists for an improved system for cooling large diameter pipes having a diameter of about four inches or more.